摘要:

July, 19511 IN COPPER-BASE ALLOYS 429 Notes MILK SOLIDS IN ICE-CREAM: A SORTING TEST THE Food Standards (Ice-Cream) Order, 1951, requires that ice-cream shall contain, among other constituents, 74 per cent. of milk solids other than fat. It has furthermore been made clear by the Ministry of Food that the expression “milk solids other than milk fat” means the total solids normally present in skimmed milk. Although the determination of lactose and ash may be a useful guide to the proportion of milk solids other than fat present in ice-cream, it does not exclude the possibility that the milk solids may have been added in the form of whey powder and not as skimmed milk solids containing a full complement of milk protein. In order to preclude this possibility when examining samples of ice-cream, it is necessary to determine the casein content, and indeed it is now our experience that the casein present in ice-cream gives the best measure of the proportion of milk solids other than milk fat that are present. The method usually employed for the determination of casein in the presence of other protein materials consists in extracting the material with a 3 per cent.solution of sodium oxalate, the casein thereby dissolved being subsequently precipitated by the addition of acetic acid. When applied to ice-cream, however, this method has been found to be rather lengthy, in that with some samples considerable difficulty has been experienced in obtaining a clear filtrate after treatment with sodium oxalate, and indeed any method involving a Kjeldahl determination of nitrogen is to be avoided in a sorting method whenever possible. Accordingly a search was made for a more rapid method for the determination of casein that might form the basis of a routine sorting test.A study of the proteins that are likely to be present in ice-cream showed that casein, the principal protein in milk, contained considerably more tryptophan than any other protein and it therefore appeared to us that the determination of the tryptophan in ice-cream might well form the basis of a sorting test. Various methods have been suggested in the literature for the determination of tryptophan in casein, and from a study of these it was considered that the method of May and Rose,l which was subsequently modified by Sullivan, Milone and Everett,2 might prove suitable for the purpose.This method consists in hydrolysis of the protein with hydrochloric acid followed by treatment with p-dimethylaminobenzaldehyde reagent, which in the presence of tryptophan gives a blue coloration. Accordingly tests were made with synthetic mixtures containing sugar, margarine, skimmed milk powder and water, and as the result of these experiments the following procedure was devised.430 NOTES [Vol. 76 METHOD REAGENTS- 100 ml of 10 per cent. v/v sulphuric acid. to 100 ml with distilled water. water. p-Dimethylarninobenzaldehyde solution-Dissolve 5 g of p-dimethylaminobenzaldehyde in Dilute hydrogen peroxide solution-Dilute 10 ml of 3 per cent. (10-volume) hydrogen peroxide Diluted hydrochloric acid-Concentrated hydrochloric acid diluted with an equal volume of PROCEDURE- Weigh 2 g of ice-cream in a 100-ml beaker, add 15 ml of water, boil gently to dissolve the starch and then cool, Precipitate the casein by the addition of 0.06 g of tannic acid, 0.5 ml of acetic acid, B.P., and 0.1 g of sodium chloride; stir, allow to stand for five minutes or until the precipitate has coagulated, and filter through a Whatman No.4 filter-paper. Wash the precipitate thoroughly with warm water, macerating or stirring the precipitate in order to assist the washing out of the carbohydrates. Pierce the bottom of the filter-paper with a glass rod and wash the precipitate into a 100-ml beaker with 50 ml of diluted hydrochloric acid (1 + 1). Place the beaker in a water-bath at 90” C for 10 minutes, then add 0.5 ml of p-dimethylaminobenzaldehyde reagent and return to the water-bath for a further 30 minutes.Remove the beaker from the water-bath, add 0.3 ml of dilute hydrogen peroxide solution and allow the blue colour to develop for a t least 30 minutes. Make the solution up to 50 ml, filter and measure the blue colour in a colorimeter or absorptiometer in a l-cm cell. Prepare a standard graph by taking ‘0.05, 0.1, 0.15, 0.2 and 0-3-g quantities of skimmed milk powder, the protein content of which has been previously determined, and treating them by the procedure described above for 2 g of ice-cream. From the graph so obtained, the quantity of milk solids other than milk fat in the sample may be readily calculated. Experience has shown that the reaction be tween p-dimethylaminobenzaldehyde and tryptophan is inhibited by the presence of carbohydrates, which give a brown colour with the reagent if they are not properly removed as describ,ed in the procedure.Traces of fat do not interfere with the reaction but larger quantities remain behind as an insoluble precipitate after treatment with hydrochloric acid and tend to slow up the development of the full blue colour. Substantial quantities of wheaten flour do not interfere with the test provided the carbohydrate is removed as described above. The only natural substances so far encountered that interfere in any way with the test are soya flour and cocoa. Soya flour gives a blue colour, but the colour deveIoped from a given weight is considerably less than that given by an equal weight of skimmed milk solids.Cocoa interferes owing to a deep reddish-brown coloration obscuring any blue colour due to casein. This unfortunately makes the test of little value with “choc-ices” unless it is possible to separate completely the chocolate from the ice-cream. Remove the fat by washing first with acetone and then with ether. REFERENCES 1. 2. May, C. E., and Rose, E. R., J . Biol. Chem., 1922, 54, 213. Sullivan, M. X., Milone, H. S., and Everett, E. I,., Ibid., 1938, 125, 471; Analyst, 1938, 63, 902. DR. BERNARD DYER AND PARTNERS LONDON, E.C.3 J. HUBERT HAMENCE G. F. J. HART May, 1951 3: 3’-DIMETHYLNAPHTHIDINE AS A REAGENT FOR THE DETECTION OF VANADIUM THE use of 3 : 3’-dimethylnaphthidine (3 : 3’-dimethyl-4: 4'-diamino-l : 1’-dinaphthyl) as a reagent for the detection of small amounts of zinc has been described in a previous communication.1 This test depends ultimately on the oxidation of the reagent to an intense red - violet product by the ferricyanide ion.We have determined the sensitivities of three of the commoner oxidising agents (Cr20,”, MnO,’ and VO,’) and the results are shown below-- As would be expected, other oxidising agents behave similarly. Limit of Concentration Ion identification limit Cr 0 I f 0.1 PLg 1 in 500,000 MAO;’ 0.5 Clg 1 in 100,000 V0,I 0.1 P.Lg 1 in 500,000July, 19511 NOTES 431 Recently, Belcher and Nutten2 have determined the sensitivities toward oxidising agents of several substituted ben zidines and related compounds. Some of these reagents were slightly more sensitive than 3 : 3’-dimethylnaphthidine towards Cr207” and MnO,’, but only one, 2 : 7- diaminofluorene, was as sensitive towards VO,’.The colour given by 3 : 3’-dimethylnaphthidine and Cr207” or MnO,’ faded after about 30 minutes, but that given by VO,’ showed no diminution in colour after standing for 24 hours. The colour given by 2: 7-diaminofluorene and VO,‘ faded shortly after development; hence 3 : 3’-dimethylnaphthidine is the most suitable amine of those examined for the detection of VO,’. Meaurio3 has previously recommended diphenylamine for the detection (and colorimetric determination) of VO,’. We have compared this reagent with 3 : 3’-dimethylnaphthidine, but the colour fades in a few minutes and the sensitivity is only 10 pg. METHOD- Reagent-A 1 per cent.solution of 3 : 3’-dimethylnaphthidine in glacial acetic acid. Procedure-Add one drop of reagent to one drop of acid VO,’ test solution (1.0 N with respect In the absence of other oxidising agents a red - to sulphuric acid) in a depression on a spot tile. violet colour denotes vanadium. REFERENCES 1. Belcher, R., Nutten, A. J., and Stephen, W. I., Analyst, 1951, 76, 378. 2. Belcher, R., and Nutten, A. J., J . Chem. SOL, 1951, 547. 3. Meaurio, V. L., Ann, chim. anal., 1918, 47, 23. R. BELCHER A. J. NUTTEN DEPARTMENT OF CHEMISTRY THE UNIVERSITY W. I. STEPHEN BIRMINGHAM, 15 January, 1951 FORMATION OF SILICOMOLYBDATE IN the course of an investigation into the colorimetric estimation of silica by means of the reduced molybdenum-blue method, i t became necessary to study the formation of silicomolybdate.Previous workers have shown that, although silicomolybdate will only form in weakly acid solution (between limits of pH 1 and pH 5 ) , it is quite stable in a strongly acid medium. This fact permits the estimation of silica in the presence of phosphate. Although phosphomolybdate will form within a wide pH range, it will not reduce to molybdenum blue in a strongly acid solution. Hence, in the presence of 0.1 N sulphuric acid, silicomolybdate will form, and if the acidity is then increased to 2 N the compound will reduce to give a molybdenum-blue colour. Phosphomolybdate (and arsenomolybdate) will not reduce if the solution is more strongly acid than 1-5 N in sulphuric acid. It is not generally recognised that in dilute solutions silicomolybdate will not form quantita- tively unless the solution is heated for some time.For accurate results, therefore, it is essential that the estimation be carried o u t in two parts, namely- (i) The formation of silicomolybdate by boiling in weakly acid solution. (ii) The reduction to molybdenum blue in strongly acid solution. Table I indicates the difference between results when silicomolybdate is allowed to form at room temperature, which is the usual procedure, and those when the heating technique is adopted. This work is being reported in full elsewhere. TABLE I DEVELOPMENT OF MOLYBDENUM-BLUE COLOUR MEASURED AS THE READING ON A SPEKKER ABSORPTIOMETER Coupling conditions 15 mins. 15 mins. 15 mins. 15 mins. 15 mins 24 hours a t 7 ° C at 15°C at 37°C a t 60°C at 100°C at 7°C A I v Test soh tion* 0.43 0.5 1 0-54 0.66 0.90 0.64 Blank without Sib’, 0.07 0.08 0.08 0.09 0.10 0.08 * A solution containing 4 p.p.m.of SO, with 0.4 per cent. of sodium molybdate in 0.1 N sulphuric acid, finally made up to 2 N in sulphuric acid before development of colour with 0-02 per cent. stannous chloride solution. 23-24 WELBECK WAY LONDON, W.l R. F. MILTON Janzsary, 195 1432 NOTES [VoL 76 THE COLORIMETRIC DETERMI NATION OF METHIONINE MCCARTHY and Sullivan' described a colorimetric procedure for estimating methionine, but the authors and others have not found it entirely satisfactory. Recently, Csonka and Denton2 thoroughly investigated McCarthy and Sullivan's nitroprusside method and, after careful experi- ments, introduced refinements that made the colorimetric estimation of methionine more practicable and accurate.We find that the modified method is still not entirely satisfactory, and that Csonka and Denton do not use sufficient hydrochloric acid to bring out the maximum red colour. Much better results are to be had by adding 2ml of concentrated hydrochloric acid in the final stage of the test. We also experienced great difficulty during the hydrolysis' of the materials, especially with the legumes that we have been investigating. With 2 ml of acid added to 0.5 g of the air-dried powdered materials, the mixtures almost invariably caked and severe bumping and even mild explosions have frequently occurred. Modifications 'were made and led to trouble-free and excellent results.METHOD Hydrolysis-Hydrolyse the materials by gently boiling 1 g of the finely powdered air-dry The hydrolysis stills are provided Instead of heating in an oil-bath,l for which material with 5 ml of 20 per cent. hydrochloric acid for 24 hours. with several water condensers arranged in series. I, 0 10 20 30 40 50 60 Transmission, Yo Fig. 1. Standard calibration curve no special advantage could be found, it is possible to heat over a small flame that just keeps the mixture gently boiling. Addition of one or two perforated glass beads helps to prevent vigorous bumping. If the mixture cakes, a small addition of 20 per cent. hydrochloric acid is made and the final volume after hydrolysis is reduced by evaporation on a bath of boiling water. Precipitation of basic amino-acids-We have found it advisable to use 100 per cent.phospho- tungstic acid for precipitating the basic amino-acids. Usually further clarification is not necessary ; if it is, decolorisation can be effected with activated carbon. After the" second centrifugation from the ice-bath, the clear supernatant fluid is carefully decanted to the last drop and neutralised to the light green colour of bromocresol green (pH 4 to 5) with 5 N sodium hydroxide, made up to a known volume (usually 8 to 10ml) and filtered through a dry filter. Development of the red colour-Four-millilitre ;tliquots of the filtrate are taken, 2 ml of 5 N sodium hydroxide and 1 ml of 1 per cent. sodium nitroprusside solution are added as in Csonka and Denton's method, the solution is warmed for 8 minutes in a water-bath at 40" C and cooled in an ice-bath for 6 minutes and then 2ml of pure concentrated hydrochloric acid are added to develop the red colour.Experiments with various volumes of different strengths of hydrochloric acid, pure concentrated hydrochloric acid, syrupy phosphoric acid and hydrochloric - phosphoric acid mixtures have shown that the addition of 2 ml of pure hydrochloric acid brings out the maximum red colour in the final solution.July, 19511 OFFICIAL APPOINTMENTS 433 Calibration cwue-A “Lumetron” photo-electric colorimeter with filter No. 530 has been used for preparing the standard calibration curve shown in Fig. 1 and for colour comparisons. RESULTS The methionine contents of the materials appear to be of the same order as those found by Csonka and Denton and appreciably lower than the values previously reported by RudraS for a modified Baernstein method.Although the Vetch pea (Lathyrus sativus) that we have examined is very rich in protein, containing 29 per cent. (other workers, Lewis, Fajans, Esterer, Chao-Wen Shen and Oliphant,* have reported a lower protein content), it contains very little methionine when compared with other legumes popular in India; even rice is very much richer in methionine. The relationship of this low methionine content of Laihyrus sativus and lathyrism is under investigation, as we believe that methionine deficiency is one of the etiological factors in human lathyrism. TABLE I Results of some methionine estimations and recoveries are shown in Table I. DETERMINATION AND RECOVERY OF METHIONINE Material Vetch pea (L. sativus) . . Moong (P. radiatus Zinn) . . Bengal gram (C. arietinum) Red gram (Cajanus indicus) Lentil (Lens esculenta) . . Rice (Oryzu sativa) . . Casein (non-dried) . . .. .. Amount of material in aliquot, g 0.52 0.40 0.43 0-20 0.50 0.25 0.05 Amount in aliquot, mg 0.3 1 1.10 1.08 0.30 1-06 0.18 0.36 Methionine A Amount in Amount Amount sample, added, found, * Yo mg mg - - 0.06 0-28 0.25 0.15 - - 0.2 1 0-07 2.0 2.16 0.72 1.0 1.40 - - - - - - Recovery of added methionine, mg % - - 1.98 99 1.04 104 * After addition of extra methionine. One of us (L. M. C.) is indebted to the Bihar Board of Medical Research for a Junior Research Fellowship that enabled him to take part in this investigation. REFERENCES 1. 2. 3. 4. McCarthy, T. E., and Sullivan, M. X., J. B i d . Chern., 1941, 141, 871. Csonka, F. A., and Denton, C. A., Ibid., 1946, 163, 329. Rudra, M. N., Current Sci., 1943, 12, 82. Lewis, H. B., Fajans, R. S., Esterer, M. B., Chao-Wen Shen and Oliphant, M., J. h‘utrit., 1948, 35, 537. DEPARTMENT OF MEDICAL CHEMISTRY LAHERIASARAI, BIHAR, INDIA DARBHANGA MEDICAL COLLEGE M. N. RUDRA L. M. CHOUDHURY

ISSN:0003-2654    

DOI:10.1039/AN9517600429

出版商:RSC    

年代:1951

数据来源: RSC

摘要:

July, 19511 OFFICIAL APPOINTMENTS 433 Official Appointments PUBLIC ANALYST APPOINTMENTS NOTIFICATION of the following appointments has been received from the Ministry of Food since the last record in The Analyst (1951, 76, 382). Public Analyst A ppointments CAHILL, Terence John (Deputy) . . .. County of Durham. LEES, Arnold (Deputy) . . . . .. . . City of Lancaster. WALKER, George Hugh . . . . .. . . City of Lancaster. OFFICIAL AGRICULTURAL APPOINTMENT NOTIFICATION of the following appointment has been received from the Ministry of Agriculture and Fisheries since the last record in The Analyst (1951, 76, 382). Agricultural A nalyst Appointment CAHILL, Terence John (Deputyj . . . . County of Durham.

ISSN:0003-2654    

DOI:10.1039/AN9517600433

出版商:RSC    

年代:1951

数据来源: RSC

摘要:

434 INTERNATIONAL COMMISSION FOR [Vol. 76 International Commission for Uniform Methods of Sugar Analysist REPORT OF THE PROCEEDINGS OF THE TENTH SESSION, 1949 THE Tenth Session of the Commission was held at the University of Brussels, Belgium, from August 15th to August 19th, 1949; sixty-three members attended representing fifteen nations. The President was Dr. Frederick Bates, U.S.A., and the Secretary was Dr. F. Todt, Germany. The world war of 1939-1946 and its aftermath imposed a gap of thirteen years between the Ninth and Tenth Sessions. Of former members many had died during this period and others were unable to attend the Brussels meeting, but a number of new members enjoyed an International Session of the Commission for the first time. During these years the scientific control of the sugar industry had continued to grow and extend and it was found necessary to place on the agenda 21 subjects for discussion as against 17 at the Ninth Session.Since previous notice of any changes in the Constitution and By-Laws had not been given, it was agreed that changes, if any, must be referred to the next meeting of the Commission, I t was felt by many members that some alternative to the title of the Commission was called for. The wide range of industrial as well as analytical problems that came under review made the present title inadequate. Reports and recommendations on the following subjects were presented. WEIGHING, TARING, SAMPLING AND CLASSIFICATION OF SVGARS- Two reports were given, one from the U.S.A. Xational Committee and one from the British National Committee.The former set out the procedural details for handling raw sugars as received from the Raw Sugar Centrals in bags or by bulk cargo, and also contained a note on the conditions of grain size and the moisture - polarisation relationships for a raw sugar to be classified as a good raw sugar from the viewpoint of the manufacturer and the refiner. Section 1 gave a summary of the rules of the Sugar Association of London, supplemented by practice at the refineries. Section 2 indicated a suggested procedure for handling raw sugar in bulk and also made proposals for mechanical mixing of raw sugar samples under appropriate at:mospheric conditions. The British Committee’s report was in two sections. DETERMINATION OF THE ASH CONTENT OF SUGAR I’RODUCTS- H.C. S. de Whalley (Great Britain) dealt with the conductometric method and the double sulphation method. Some modifications in each method were described and a number of recom- mendations made, including one to discontinue the 10 per cent. deduction from sulphated ash. * Obtainable from the British Standards Institution, Sales Department, 24, Victoria Street, London, S.W.1. t Printed in England and published by the International Commission for Uniform Methods of Sugar Analysis. Chairman, Publication Committee: Lewis E.ynon, 7 and 8 Idol Lane, London, E.C.3. 1050. Price 5s. Issued as a Supplement to The International Sugar Journal, June-July, 1950.July, 19511 UNI%9R METHODS OF SUGAR ANALYSIS 435 Proposals for further work were suggested and the paper included a useful summary of recent literature.H. E. C. Powers (Great Britain) compared gravimetric with conductivity ash measured at different degrees Brix and graphs are reproduced showing the resistance - Brix relation at different ash contents and the per cent. ash - C ratio. In the discussion, J. Vernon (Australia) observed that the suggestion to discontinue the 10 per cent. deduction from sulphated ash would affect the basis of payment for raw sugars in Australia, which is based on net rendement. DETERMINATION OF REDUCING SUGARS- The report surveyed a number of methods used throughout the sugar industry for the deter- mination of invert sugar in refined sugars, raw beet sugars, beet molasses and cane sugars of low invert content. Ofner’s method as modified by Jackson and McDonald gave increased repro- ducibility and yielded results of the same precision as that of the Berlin Institute method.C. A. Fort had extended the scope of the Lane and Eynon method to include more dilute solutions than those used by the authors. The ccnvenient and rapid routine control method devised by H. C. S. de Whalley was referred to for the determination of invert sugar in refined white sugar. The U.S.A. committee would appreciate any information concerning modifications of the methods referred to in their report. They recommend studies to be made (a) comparing the modified Ofner’s method with the modified Lane and Eynon’s method for small amounts of invert sugar in presence of sucrose and (b) on the necessity for defecating specific products, the most suitable defecant and the procedure for removing unused defecant.L. Eynon and J. H. Lane (Great Britain) presented a very useful note on the preparation of a stable solution of invert sugar the titre of which will remain constant permanently. STANDARD TESTS FOR THE PERFORMANCE OF BONECHAR AND DECOLORISING CARBONS- G. P. Meade (U.S.A.).read the report of V. R. Deitz which summarised a survey of the existing test procedures, fifteen of which had been selected for study by the Bonechar Research Project, Inc. An example was given of the proposed investigation on one of the items, “Chemical Analysis for Sulphur in Bonechar. ’’ At the present session the report stated that not even a tentative procedure could be submitted for approval on decolorisation and ash removal tests, but it was anticipated that a report could be reasonably expected at the next meeting.At the Ninth Session (1936), K. Smolenski had made some specific recommendations in the test for decolorising power and Kurt Lijwy (Brazil) communicated some pertinent comments on these earlier proposals. G. W. Payne (Great Britain) examined the standard method for decolorising power adopted at the Ninth Session in special reference to particle size, the importance of which was not previously recognised. This paper also gave details of an improvement in the method of bulk sampling of deliveries of new char. TESTING OF MOLASSES AND SUGAR SYRUPS- J. G. Maltby (Great Britain) referred to the Ninth Session recommendations and suggested certain changes under the following heads: (a) Replacement of optical by chemical methods for sucrose, (b) total sugar as invert sugar, (G) Lane and Eynon constant volume method for reducing sugars and ( d ) fermentable and unfermentable sugars.(a) Chemical methods were now used almost exclusively in Great Britain; they obviated some of the sources of error in the Clerget method and offered certain advantages. On average the Clerget method gave rather high results for sucrose. For accuracy, invertase should be used in preference to acid inversion, but for certain types of control the simpler acid inversion was sufficient. (b) Although for Customs purposes in Great Britain duty was levied on the sum of the sucrose and reducing sugars, for calculating yields of yeast and alcohol both sugars should be expressed in the same units and one determination by the chemical method of the total sugars, as invert sugar, was all that was required.Normally no clarification was necessary. ( c ) This modification had been in use in the Customs Laboratory for many years but had not been published. Its great advantage was that it dispensed with the Lane and Eynon tables. One method of the constant volume modification was described and others were in use in various laboratories. When sucrose was present a different factor must be applied; factors were given for sucrose ranging from 0 to 12-6 g present in reaction flask. ( d ) These figures would be useful, but no published436 INTERNATIONAL COMMISSION FOR [Vol. 76 method was suitable for routine testing.The referee was carrying out an investigation and suggested that this should be a new subject for the next session. H. C. S. de Whalley gave details of the chemical method of determination of sucrose with invertase solution on behalf of the British National Committee. He also recommended that defecation should be dropped and that treatment with potassium oxalate solution only (to remove lime salts) was sufficient to give a clear end-point and good agreement. During discussion it was stated that the differences between sucrose by Clerget and sucrose by the chemical method using invertase varied according to the product under examination; for dark coloured materials the random error when using the chemical method is smaller. Jackson and Gillis No.IV method (polanmetric) gives the nearest agreement with the invertase chemical method. The U.S.A. sub-committee on this subject circulated a detailed summary of recommended methods for (1) Sucrose in Cane Molasses and Syrups, (2) Reducing Sugars in Cane Molasses, (3) Sucrose and Raffinose in Beet Molasses, (4) Reducing Sugars in Beet Molasses and (5) Weight per gallon of Molasses and Syrups. J. Vernon gave a summary of the methods used in this con- nection by the Colonial Sugar Refining Co. of Sydney. In discussion, G. P. Meade referred to the differences caused by the various methods of preparation of the solutions. REFRACTIVE INDICES OF SOLUTIONS OF SUCROSE, DEXTROSE, LAEVULOSE, RAFFINOSE, INVERT C. F. Snyder (U.S.A.) reviewed the work on this subject accomplished at previous sessions, notably the Eighth and Ninth.It was Considered essential that accurate values on indices of sucrose to five decimal places over the entire range be made available in order to utilise fully the precision of modem refractometers. At present such data exists only up to 24 per cent. of sucrose and further study should be given to the ra,nge of 25 to 85 per cent. sucrose solutions. As regards the refractive indices of solutions of other sugars, the Committee's recommendations as the most accurate values a t present available were (a) Zerban and Martin for dextrose at 20" C, (b) Zerban and Martin for invert sugar a t 20" C and ( c ) Jackson and Mathews for laevulose a t 20" C as re-calculated by the Saunders equation. Further study was suggested for the refractive indices of raffinose and for the application of refractometric methods to the analysis of mixtures.H. C. S. de Whalley read a paper on the Refractometric Solids of Sugar Syrups containing Invert Sugar. In the past, corrections on account of invert sugar had been made on the basis of varying degrees Brix and also on the basis of the invert sugar content. It was now proposed that the correction formula for commercially prepared syrups containing reversion products should be y = O.O0025x, where x equals the true or corrected solids. For low invert contents the observed solids can be used in the formula without serious error. He preferred no lead defecation but de-calcifying with oxalate. SUGAR AND MIXTURES- STANDARDISATION OF QUARTZ CONTROL PLATES- Reference was made to the recommendations on this subject at the Eighth and Ninth Sessions.The question now brought forward was the correlation of the a,ttested sugar value, S,,, of an international plate valid a t 20" C and a sugar value, St, such that St serves as a control of the International Sugar Scale used a t to C. The following equation had been proposed by the Deutches Amt fur Mass und Gewicht, to which the work of the former Reichanstalt in the Eastern Zone of Germany had been transferred- A table based on this equation was presented for the range 7" to 33" C, and a second table of correction factors to be applied to the polarisation of the normal solution of sucrose when the temperature of the solution (tl) differs from the standard temperature t marked on the brass normal weight, on the flask, and on the normal tube of glass.It was recommended that the four National Physical Laboratories of the U.S.A., Great Britain, France and Germany should collaborate in an intercomparison of interchanged national sets of control plates for testing the validity of the above proposed equation and the tables based thereon. Dr. E. Einsporn (Germany) contributed a paper which was read by Dr. F. Todt. St = S,o[l + 0.000322 (t - 20) - 0*00000279 (t - 20)2] SPECIFICATIONS FOR THE EVALUATION OF THE REF;"ING QUALITIES OF RAW BEET SUGAR- A report was presented by the Danish Sugar Co. The suitability of raw beet sugar for refining For the should be considered with regard to the untreated sugar as well as to the affined sugar.July, 19511 UNIFORM METHODS OF SUGAR ANALYSIS 43 7 former, the yield, storage quality, colour and bacteriological tests were recommended.As regards the affined sugar, a standardised treatment was described in some detail for determinations of ash, water, pH and alkalinity, invert sugar, colour, affination, turbidity and size and uniformity of grain. The tests for size and uniformity of grain as determined by using special sieves were somewhat similar to those published in 1948 by H. E. C. Powers (Great Britain), who gave a report on grist or grain size. His report described the technique of a method whereby the grain size was repre- sented by a numerical index for the M.A. (mean aperture) and uniformity by an index for the C.V. (coefficient of variation).Standard glass plates had been prepared on which synthetic mixtures of sugar of pre-determined M.A. and C.V. have been set in a coating of transparent wax. An adequate series of such plates could supplant the whole gristing tests and, if carefully handled, could be used for an indefinite time. If an unknown sugar was spread similarly upon a glass plate and examined either by the unaided eye or by a binocular magnifier and compared with the standard plates, the correct M.A. and C.V. could be interpolated with surprising accuracy. METHODS FOR THE EVALUATION OF THE REFINING QUALITIES OF RAW CANE SUGAR- H. I. Knowles (Canada) stated that among the refining qualities of interest to the refiner and for which methods of evaluation are available, are the following: (1) grist or crystal size, (2) crystal purity, (3) water insoluble matter, (4) filtrability, ( 5 ) colour and (6) soluble ash.Each of these was referred to in the report and details of methods proposed for the first three were given very fully. It was recommended that these three methods be subjected to collaborative study and that further work be undertaken to investigate the Bomb Filterleaf for the Elliott filtrability test on the lines described in the report. The Danish Sugar Company presented a report describing an apparatus they have devised for the direct determination of filtrability. The time in seconds taken to filter, under constant pressure, a pre-determined volume difference is measured and an equation is given relating the coefficient of filtration, FK, with the difference in time taken.A factor, q, which is tabulated, involves the filtering area and the size of the intervals. SPECIFICATIONS AND TOLERANCES FOR PURE PRODUCTS- (a) Sucrose for verifying the saccharivneter scale-L. Eynon and J. H. Lane (Great Britain) observed that great progress in refinery technique had made it possible to obtain directly sugar that could be safely assumed to have a sucrose content of not less than 99.99 per cent., a degree of purity more than sufficient for standardising the saccharimeter. They recommended the use of this sugar for purposes of standardisation as preferable both as regards purity and convenience to the lengthy purification processes prescribed at the Third Session held in 1900. A technical note on details of preparation of such highly refined sugar and methods of test was given by H.C. S. de Whalley. The sub-committee of the U.S.A. National Committee presented a specification for pure sucrose. (b) Basic lead acetate solution and (c) dry basic lead acetate-The U.S.A. sub-committee presented specifications based on the American Chemical Society’s specifications for both these reagents. The Australian specification for (c) permits a slightly lower limit for the basic lead (PbO) content. The pure refinery sugar just referred to was well within the recommended tolerances. SPECIFICATIONS FOR TESTS FOR THE EVALUATION OF THE CRYSTALLISING QUALITIES OF BEET AND Two reports were presented, one by the U.S.A. National Committee and one by the Danish Sugar Company; the former suggested study on a method based on the residual purity or concentration of a syrup of predetermined standard concentration that has been treated with a standard quantity of seed and cooled over a prescribed schedule. Although the preliminary work would be large the comparative simplicity of the whole operation made the method appear attractive.The Danish Sugar Company’s report included a mathematical treatment of the methods of de Vries and Kucharenko and deduced an expression relating the rate of crystallisation (K) with the increased weight of the seed crystals. Graphs are given and viscosity curves have been introduced in the graphs. Determination of K using varying sizes of crystals had shown good agreement. CANE SUGAR FACTORY JUICES- This subject is one on which no previous recommendations have been made.The effect of viscosity also required close study.438 INTERNATIONAL COMMI[SSION FOR [Vol. 76 COLORIMETRY, NEPHELOMETRY, REFLECTOMETRY AND FLUORESCENCE IN THE SUGAR INDUSTRY- 0. Wiklund (Sweden) presented a long report that has been published in full elsewhere and made a number of recommendations. These included a statement of units, terms and symbols to be used in colorimetry when results of spectrophotometric absorption measurements on sugar solutions are reported. H. C. S. de Whalley read a paper on the preparation of solutions for colorimetry. For filtration he stressed the necessity for very high grade kieselguhr that has been previously treated with sulphuric acid to remove fine kieselguhr particles. Neutralisation with soda solution should follow.The term “colour” of a sugar solution required definition and he proposed that it should be the absorption at 560 mp of solution filtered with specially prepared “Dicalite Superaid” under standard conditions. The absorption of colour by kieselguhr had been over-emphasised. VALUES OF THE CLERGET DIVISOR AND METHODS FOR MULTIPLE POLARISATION- The long and valuable report on this subject by the referee (Dr. F. W. Zerban) is ably sum- marised in the Proceedings. Investigatory work done since 1936 (some of it privately communicated to the referee) is dealt with. The most recent values of the divisor for different temperatures of inversion are given and also the re-determined values for the coefficients of concentration and reading temperature.Inversion by acid and by invertase is examined and the effect of salts and other non-sugars on the Clerget divisor is referred to. As regards the determination of sucrose and raffinose in beet products, the referee comments on the two-enzyme method of Paine and Balch and also on the method of Osborn and Zisch, which is based on the observation that the optically active non-sugars become inactive in strongly acid solutions. Twelve recommendations were submitted for appropriate action. A report by H. C. S. de Whalley and N. Albon was presented. This report gave an account of the detection and estimation of raffinose in raw beet sugars by a method of paper chromatography. The introduction of this technique enabled amounts of raffinose as low as 0.05 per cent.to be detected. The method was under active investigation and development at the time of the Brussels meeting. DETERMINATION OF DRY SUBSTANCE I N SUGARS AND SUGAR PRODUCTS- The referee’s report contained a critical surve:y of available methods; these were classified under six groups : (1) density, (2) refractive index, (3) distillation with immiscible solvent, (4) drying at atmospheric pressure, ( 5 ) vacuum oven at low temperatures and (6) Karl Fischer titration. The special requirements and merits of each method were reviewed. Special attention was drawn to a recent paper by Iles and Sharman where it was shown that the loss of carbon dioxide that occurs in moisture determination by the reaction between amino-acids and reducing sugars was also dependent on ventilation. DETERMINATION OF THE HYDROGEN-ION CONCENTRATION OF SUGAR FACTORY PRODUCTS- The referee (H.E. C. Powers), after reviewing the types of equipment now available for pH determinations and commenting on various electrodes recommended that, for official reports, pH in sugar products shall be accepted as that obtained when using a set equipped with a suitable glass electrode a t 20” C (or 28’ C) standardised with the National Bureau of Standards buffers 4.005 and 9.20 pH, all products being tested at existing degrees Brix. As regards correction for temperature, this was not possible since the effect varies with different products. An interim report by D. Gross (Great Britain) covering this subject gave an account of some research work still in progress.Determinations of pH over the temperature range 20” to 80°C had been made on standard buffer solutions and certain cane sugar liquors. The temperature effect on the pH of these solutions and liquors varied from very slight to very marked and the results warranted systematic investigation. ’The research would not be restricted to 80’ C as the upper limit. C. L. Hinton (Great Britain) read a report on the buffering effect of sugars and described a titration method using 0-1 N hydrochloric acid anti a stock buffer solution whereby the buffer power of the sugar at pH 4.0 could be rapidly determined. ANALYSIS AND EVALUATION OF REFINED SUGARS- The referee (G. P. Meade) remarked that although there was little commercial demand for the chemical testing of refined sugars, there was a growing interest for a standard procedure for evaluating the quality of this product.Primarily tests of physical characteristics were calledJuly, 19511 UNIFORM METHODS OF SUGAR ANALYSIS 439 for, such as colour and turbidity of solution, crystal size, moisture, foaming tests, volume weight and sediment. A number of tentative recommendations were made together with suggestions as to special applicability to refined sugars of tests previously described for the evaluation of the refining qualities of raw beet and raw cane sugar. A method for the determination of starch in powdered sugar was described and a second report was presented on refined sugar evaluation and analysis by the Danish Sugar Company, dealing with ash, colour, turbidity, "redness,' and grain size.DESIGN AND STANDARDISATION OF LABORATORY APPARATUS- Sub-committee is included in the Proceedings. No report was submitted to the Commission, but a summary of the report of the U.S. National DETERMINATION OF VISCOSITY AND SURFACE TENSION OF SUGAR SOLUTIONS- The report presented on this subject was the approved report of the U.S. National Committee together with some supplementary notes. It contained a review of the literature on the viscosity and surface tension of molasses and sugar solutions and some recommendations on experimental methods. A brief review of the surface tension of solutions of sugars and sugar products by A. Van Hook is also included. STANDARD METHOD FOR THE DETERMINATION OF ELECTRICAL CONDUCTIVITY OF SUGAR SOLUTIONS- No report was submitted; it was agreed that the subject should be deleted from the programme.REDUCTION OF THE LEAD ERROR IN POLARISING RAW SUGARS- A. H. Rheinlander (Great Britain) referred to the Ninth Session where the British delegation had expressed their disagreement with the recommended use of dry lead for clarification. He presented a report summarising the conclusions reached after a further study on the comparative polarisations of cane raws by the wet and dry methods. Several members of the British National Committee had collaborated in practical work, details of which were set out in the report. It was observed that the British sugar industry was largely concerned with raws polarising about 97" S and a t this point the difference between the wet and dry methods was of the same order as the sensitivity of the ordinary laboratory saccharimeter, i.e., FO.05" S.A number of practical reasons were given for preferring the use of lead solution and the British National Committee concluded (1) that the continued use of the wet method was justified and (2) that the 100" point of the saccharimeter should be divorced from any question of lead defecation. G. W. Payne in a second paper set out the statistical analysis of a number of polarisations of raw sugars examined by the two methods. The mean difference for British West Indian raws was 0-033" S and for Cuban raws 0.064" S. The average polarisation of both sets of sugars was approximately the same and the effect of the country of origin on the mean difference was observed with interest. The cumulative effect of the small polarisation difference between the two methods would, over a period, have a significant effect on the value of raw sugar cargoes. Attention should be turned to the minimum use of lead and to this end a high level of saccharimeter illumination is perhaps the most important factor. The U.S.A. delegation recommended, inter &a, the continuance of the dry method as official. If the wet method were used the reading should be corrected by the subtraction of 0.1" S. H. C. S. de Whalley suggested that the correction should be graded. The use of dry lead was supported by a letter from K. Sandera (Czechoslovakia), by J. Vernon (Australia) and by J. Ancizar-Sordo (Columbia). The wet method was favoured by F. W. Hayes (South Africa) and by C. L. Hinton (Great Britain). A. H. Rheinlander opposed a sliding scale of corrections as cumbrous and inexact. Polarisation was an arbitrary figure having no precise scientific meaning, but was commercially of great importance. A letter was read from K. Lowy (Brazil) advocating clarification with lead solution and de- leading with sodium oxalate before making to volume. A correction was then applied to the polarisation reading dependent upon the volume of lead solution added. The referee commented on this proposal. The discussion that followed these papers was lively and prolonged. The Proceedings print full references for all the papers quoted. The next session of the Commission was fixed for 1953 in Paris. -4. H. RHEINLANDER

ISSN:0003-2654    

DOI:10.1039/AN951760434b

出版商:RSC    

年代:1951

数据来源: RSC

摘要:

440 BOOK REVIEWS [Vol. 76 Book Reviews TEXTBOOK OF QUANTITATIVE INORGANIC ANALYSIS. By I. M. KOLTHOFF and E. B. SANDELL. This textbook was first published in America in 1936 and was favourably reviewed in The Analyst (1937, 62, 697-698) by. S. G. Clarke, who adequately described its character and scope. A revised edition, enlarged by forty-five pages, appeared in 1943 with the subject-matter and its organisation essentially the same as in the first edition. The present volume is merely a reprint of this revised edition and is labelled, pointlessly and unnecessarily, the First English Edition. As the revised work was not reviewed in The 14naZyst, i t is worth while mentioning some of the changes that have been made. A fuller description of organic reagents, eight more well- known reagents being dealt with, and a table showing the empirical formulae of the 8-hydroxy- quinoline complexes of the metals, their pH ranges for complete precipitation, and the chief literature references are given.Curiously enough, dithizone is not mentioned in this section, but amends are made in the chapter on Colorimetry and Spectrophotometry, which has been enlarged by nine pages devoted to photo-electric methods. Electro-titrations now include a five-page discussion of amperometric titrations. The chapters on the theory of electro-analysis, on the formation and properties of precipitates arid on co-precipitation phenomena have been revised, the section on the ageing and filterability of precipitates being largely re-written. The interesting chapter dealing with Errors in Quantitative Analysis has also been expanded and revised.The statement that 15” C is the standard temperature in England for the calibration of volumetric glassware (see Clarke, loc. czt.) has been removed from the revised edition, but the one (p. 635) that quadrivalent t i n is reduced by zinc to the bivalent form has not, unfortunately. Another error that occurs in all three printings of the book is that, in Allen and Bishop’s method for determining sulphur in pyrites, the original instructions are that the solution of barium chloride should be added without stirring and not with stirring, as the present authors say. In their preface, the authors ask for further suggestions to improve this book, and I suggest that, in determining carbon dioxide in limestone (p 386), they should abandon the use of hydro- chloric acid for decomposing the mineral.By using syrupy phosphoric acid instead, they would not only obtain a better attack on the mineral, but they could also simplify the apparatus by using a smaller vessel to contain the sample and by leaving out the unwieldy condenser. The blank for a determination in an apparatus simplified in this way can easily be reduced to about 0.5 mg. The book is one that can be safely put into a student’s hands and any student who wants to learn something of the theoretical background of analytical chemistry will find here much to interest and instruct him. L. S. THEOBALD Pp. xvii + 794. London: Macmillan & Co., Ltd. 1950. Price 30s. net. TECHNOLOGY FOR SUGAR REFINERY WORKERS.By OLIVER LYLE. Second Edition. Pp. 525. Although this is a second and enlarged edition of a book that “was written primarily for the Plaistow Wharf staff,” as stated in the author’s foreword to the 1941 edition, its appeal is very much wider. The description of sugar refining should be of interest to all who like to know some- thing of the processing of their daily food. For the young technician, be he chemist, physicist or engineer, there is a wealth of well-presented information on a wide range of subjects. The style of writing is lucid and explanations are in the simplest possible words, so that, although it is not a “popular science” book, it is as suitable for the general reader as for the trainees for whom it was intended. The subjects range from an introduction to sugar and the sugar cane, through chapters of general application that give concise pictures of the measurement of physical quantities, an outline of basic chemistry, general methods of analysis, steam generation and use, and electricity, to chapters more specifically pertinent to the sugar industry.This is covered by chapters on special pumps for circulating liquors, vacuum pans, evaporators, methods of filtration and purification. Chapters on the commercial side of the industry, the control and planning of processes, financial balance sheets, the balancing of heat input and work done, the balance between sugar input and output and, more generally, the planning of experiments should be read by all those scientists London: Chapman and Hall Ltd.1950. Price 32s. net.July, 19511 BOOK REVIEWS 441 who have as yet had little experience in the control of industrial processes. The importance of the sugar balance is underlined by the work recently reported in The Analyst (1951, 76, 287) on the effect of the presence of raffinose on the determination of sucrose by the standard methods. The features include illustrations accompanied by sufficiently full captions to allow them to be understood without reference to the main text; although this means some duplication of matter, extraordinary clarity of exposition has been achieved. The diagrams are clearly drawn. The author has avoided the more hackneyed illustrations of physical phenomena. Instead of the cohorts of soldiery who march through sand to illustrate the laws of refraction and total internal reflection, Mr.Lyle makes use of a car (pp. 38 and 39), possibly produced by his neighbour at Dagenham. Apt quotations appear at the head of each chapter and elsewhere; they range from the Tate and Lyle motto from Judges xiv. 14, through Horace (“He seeks to produce not smoke from light but light from smoke”) to Shakespeare’s “And we must take the current when it serves, Or lose our ventures” (Julius Caesar)-particularly appropriate in times of electrical “load-shedding.” Lewis Carroll’s classic is represented by the Hatter’s remark to Alice about the contents of treacle wells (at the beginning of the chapter on pumps) and by other quotations. The direct style of the writing, which avoids such “padding” words as “however” and “there- fore,” is to be commended; it is a matter of regret that sometimes the ordinary laws of syntax have been broken and that sometimes the diction is loose.There is an unhappy sentence on p. 228, where we learn that “The water needed by a jet condenser is given in Table VI.” In the effort to clarify the complicated subject of polarised light, an error has crept into the description of the Nicol prism, p. 77. The author states that light, on entering the prism, “is refracted into two rays, ordinary and polarised,” and both text and diagram imply that the former is unpolarised. The Ordinary ray in calcite must, of course, be polarised to the same extent as the Extraordinary ray, although the planes of polarisation are mutually perpendicular.The nomenclature of the rays derives from their behaviour in respect of their refractive indices: the Ordinary ray in calcite has a constant refractive index ( w ) of 1.66 for travel in any direction through the crystal, while the refractive index ( E ) for the Extraordinary ray varies from a minimum of 1-48 to a maximum equal to w according to the direction the ray travels in relation to the optical axis of the crystal. In the direction of travel in a Nicol prism the particular value of c is 1.534, approximately equal to the refractive index of the Canada balsam cement joining the two halves of the prism. Thus it is purely a matter of convenience that the Extraordinary ray passes through while the Ordinary ray is totally internally reflected and then absorbed in the black wall of the prism container.The few slips noticed above and about a dozen misprints seen during a careful and highly profitable reading of this book should not affect its value. I t is commended to the general and technical reader alike. The book itself is well produced. J. B. ATTRILL THE IDENTIFICATION OF MOLECULAR SPECTRA. By R. W. B. PEARCE, D.Sc., F.R.A.S., and A. G. GAYDON, D.Sc. Second Edition. Pp. xi + 276, with 12 Plates. London: Chapman and Hall Ltd. 1950. Price 50s. The second edition of this book of tables of wavelengths of the bands in molecular spectra brings the original volume, published some ten years ago, up to date. This work of reference should prove its usefulness in scientific establishments and should be particularly valuable where spectrographic studies are carried out, especially so where the hollow cathode technique is being employed.It should form a companion volume to the M.I.T. tables of Harrison and used in conjunction therewith it should be possible to establish beyond doubt whether nebulous lines are in fact atomic lines or molecular band heads. The book gives a general table of all persistent band heads in order of wavelength before proceeding to a more detailed treatment of individual systems classified under the particular molecule producing them. Ample references are included for anyone who requires to make a more detailed study. A short dissertation on practical details of the identification of band spectra and the use of the tables is included, together with a description of various methods that may be used for their excitation.442 INTERNATIONAL COMMISSION FOR [Vol.76 Finally, for th,e twelve plates of spectra, the authors deserve special credit. The photographic reproduction of spectra is a matter of some difficulty and is often very indifferently carried out. In this book, not only have these plates been excellently reproduced but in addition they are well annotated, which makes them a really valuable appendix t o the tables. This volume has been clearly printed, well set out and handsomely bound, producing a book of a quality all too rare in publications of this ccluntry. It should find a place in all properly equipped scientific libraries. J. A. C. MCCLELLAND SYSTEMATIC ORGANIC CHEMISTRY. By W. M. CUMMING, I. V. HOPPER and T.S. WHEELER. Fourth Edition. Pp. xxviii + 556. London: Constable and Co. 1950. Price 37s. 6d. The first edition of this book (1923) aimed at being “more than a collection of recipes” and it was hoped that through it “purely theoretical books would take on a new meaning” for the student. The word “systematic” was used in the title because reaction followed reaction on a definite plan. The sub-title “Modern Methods cd Preparation and Estimation” removed any ambiguity as to the scope of the work. The appeaxance of a fourth edition, revised and enlarged, shows that the book occupies a niche of its own. The price, although very reasonable for a book of this size, is not low for the student’s pocket. It is claimed on the dust-jacket that all sections of the book have been modernised and extended “so as to include all the more important develop- ments that have taken place during the last decade.” The reactions associated with the names of Diels and Alder, Fischer and Tropsch, Hinsberg, Kharasch, Markownikoff, Ponndorf and Zerewitinoff are included, and so also are oxidations with lead tetra-acetate and periodic acid.The Rast method for determining molecular weight is described, but nothing is said about its limitations nor is any alternative mentioned. The Girard reagents do not find a place. Much progress has been made in recent years in organic chemistry in the field of natural products, in improved isolation procedures and degradations. A systematic treatment of organic chemistry from the point of view of practical techniques ought to place some emphasis on physical methods.Photo-electric colorimetry and ultra-vj olet and infra-red spectrophotometry are not considered and chromatography gets not quite one page. These techniques together have radically affected many aspects of the quantitative analysis of organic substances. As a guide to preparative organic chemistry the new edition fully maintains its high reputation, b u t the revision fails to reflect the movement of new techniques from the periphery to nearer the centre of organic chemistry. There is a substantial and well-written new chapter on micro-analysis. R. A. MORTON ORGANIC REACTIONS. Volumes I to V. Edited by ROGER ADAMS, W. E. BACHMANN, A. H. BLATT, L. F. FIESER, J. R. JOHNSON and H. K. SNYDER. Pp. vii + 391; v + 461; viii -+ 460; viii + 428; viii + 446.New York: John Wley and Sons, Inc. London: Chapman and Hall, Ltd. 1942, 1944, 1946, 1948, 1949. Price: 44s., 44s., 48s., 48s., 48s. This series has now established itself as a compendium that is all but essential to the practising organic chemist. Forty-eight reactions are described from the preparative viewpoint ; each chapter deals first with the general nature of the reaction under consideration, then, critically, with its scope and limitations and with typical experimental conditions, including full preparative details for selected products, and finally gives a comprehensive list of examples with full literature citations. Apart from the chapters of obvious analytical interest, e.g., those on periodic acid oxidation (Volume 11), the reactions of thiocyanogen (Volume 111) and the Diels - Alder reactions (Volumes IV and V), the analyst will find this series of value in two ways; first, for deciding what analogues of known organic reagents are likely to be readily prepared and so worth studying as alternatives to known reagents and, secondly, for devising new methods of organic analysis, since it cannot be doubted that many of the preparative methods so thoroughly surveyed in this series can be made the basis of analytical procedures.H. N. RYDON DIE THEORETISCHEN GRUNDLAGEN DER ANALYTISCHEN CHEMIE. By GUNNAR HAGG. Translated into German by H. BAUMANN. First Edition. Pp. 197. Basle: Birkhauser AG. 1950. Price 22fr. A work by Professor Hagg must necessarily command respect and this book will surely capture The subject-matter is not unfamiliar, but is presented in an An immense amount of material is dealt with in the space available, the admiration of all who read it. eminently refreshing manner.July, 19511 PUBLICATIONS RECEIVED 443 and this is accomplished without recourse to misleading simplifications or half truths and without reducing the text to a mere collection of equations, for there are many examples of the applications of the principles laid down. Naturally, the book is mainly concerned with electrolyte equilibria, but precise and useful chapters are included on adsorption and colloids, and on the properties of precipitates. Bronsted’s definition of acids and bases is used throughout, but the less familiar terminology that this involves should present no difficulties. A book of this type has long been needed; for so many books published on quantitative chemical analysis attempt to cover both theory and practice, with the result that the theoretical section is usually quite inadequate. Thanks are due to Dr. Baumann for making this book available to all chemists. A set of problems (with answers) is provided. The publishers are to be congratulated on a high standard of production. J. F. HERRINCSHAW

ISSN:0003-2654    

DOI:10.1039/AN9517600440

出版商:RSC    

年代:1951

数据来源: RSC

摘要:

July, 19511 PUBLICATIONS RECEIVED 443 Papers for Publication in THE ANALYST THE Editor welcomes Papers and Notes for insertion in The Analyst, whether from members of the Society or non-members. They are submitted to the Publication Committee, who decide on their suitability for insertion or otherwise. A copy of the current Notice to Authors, reprinted from The Analyst, 1951, 76, 385, can be obtained on application to the Editor, The Analyst, 7-8, Idol Lane, London, E.C.3. All Papers submitted will be expected to conform to the recommendations there laid down and any that do not may be returned for amendment.

ISSN:0003-2654    

DOI:10.1039/AN951760443b

出版商:RSC    

年代:1951

数据来源: RSC

摘要:

LOCAL SECTIONS AND SUBJECT GROUPS THE North of England Section and the Scottish Section were formed to promote the aims and interests of the Society among the members in those areas. Members of the Society residing in England or Wales north of Birmingham may become members of the North of England Section and those resident in Scotland members of the Scottish Section. The Microchemistry Group, the Physical Methods Group and the Biological Methods Group have been formed within the Society to further the study of the application of micro- chemical, physical and biological methods of analysis. All members of the Society are eligible for membership of the Groups. There is no extra subscription for membership of a Section or Group. Application for registration as a member should be made t o the Secretary. The Sections and Groups hold their own meetings from time to time in different places.

ISSN:0003-2654    

DOI:10.1039/AN951760444b

出版商:RSC    

年代:1951

数据来源: RSC